Organic electroluminescence elements (organic EL elements) have been used as self-luminous elements for image display devices such as displays, and for surface light sources. Such an organic EL element (Organic Light Emitting Diode: OLED) is generally fabricated by stacking a transparent electrode serving as an anode, an organic layer, and a metal electrode serving as a cathode in this order on a transparent supporting substrate such as a glass substrate or a transparent plastic film. Thus, upon application of a voltage between the transparent electrode and the metal electrode, electrons supplied from the cathode and holes supplied from the anode are recombined at the organic layer. Then, when excitons generated by the recombination change from an excited state to a ground state, EL emission occurs. Light of the EL emission goes through the transparent electrode, and is extracted to the outside on the transparent supporting substrate side.
However, such an organic EL element has a problem that the light generated at the organic layer cannot be extracted to the outside sufficiently. Specifically, the problem is that a large proportion of the light generated at the organic layer disappears as heat during repetition of multiple reflections in the element, or propagates inside the element and exits from end portions of the element, so that a sufficient external extraction efficiency cannot be achieved.
To solve the problem, for example, International Publication No. WO2011/007878 (WO2011/007878: PTL 1) discloses an organic EL element comprising: a transparent supporting substrate (A); a cured resin layer (B) staked on the transparent supporting substrate; and a transparent electrode (C), an organic layer (D), and a metal electrode (E), which are stacked in this order on the cured resin layer (B), wherein the cured resin layer (B) has concavities and convexities on a surface thereof, and a shape of the concavities and convexities is such that when a Fourier-transformed image is obtained by performing two-dimensional fast Fourier transform processing on a concavity and convexity analysis image obtained by analyzing the shape of the concavities and convexities by use of an atomic force microscope, the Fourier-transformed image shows a circular or annular pattern substantially centered at an origin at which an absolute value of wavenumber is 0 μm−1, and the circular or annular pattern is present within a region where an absolute value of wavenumber is within a range of 10 μm−1 or less. In addition, Hideo Takezoe et al., “Enhanced Light Extraction Efficiency of Organic Light Emitting Diode using Microlens based on Buckling Phenomenon” described on p. 12-345 of “Proceedings (NPL 1)” of The 57th Meeting of The Japan Society of Applied Physics and Related Societies issued in 2010 discloses that an ultraviolet-cured resin having a concavity and convexity shape is formed by a nanoimprinting method using a polydimethylsiloxane (PDMS) in which a concavity and convexity shape is formed by a buckling phenomenon, and this ultraviolet-cured resin is used as a microlens for an organic EL element.
The organic EL element described in PTL 1 and the organic EL element using the microlens described in NPL 1 have sufficiently high light extraction efficiencies. However, there is a demand for development of an organic EL element whose angle-dependence of luminance and change in chromaticity are sufficiently reduced at higher levels.